Binder-free high strength, low steam-to-oil ratio ethylbenzene dehydrogenation catalyst

ABSTRACT

The invention discloses a binder-free high strength and low steam-to-oil ratio ethylbenzene dehydrogenation catalyst, which is characterized by comprising the following components in percentage by weight:
         (a) 60-85% Fe 2 O 3 ;   (b) 3-25% K 2 O;   (c) 0.1-5% MoO 3 ;   (d) 3-20% CeO 2 ;   (e) 0.1-5% CaO;   (f) 0.1-5% Na 2 O;   (g) 0.1-5% MnO 2 , wherein the weight ratio of sodium oxide to manganese dioxide is 0.1-10;   (h) 0.1-100 ppm of at least one element or oxide of Pb, Pt, Pd, Ag, Au, Sn; and no binder is added during the preparation of the catalyst. The low steam-to-oil ratio ethylbenzene dehydrogenation catalyst provided by the present invention contains no binder and maintains high strength, and has high activity and stability at low steam-to-oil ratio.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Chinese Patent Application No.201710269815.3, filed Apr. 24, 2017, which is incorporated herein byreference in its entirety.

TECHNICAL FIELD

The present invention relates to the technical field of alkylaromatichydrocarbon dehydrogenation catalyst, in particular to a binder freehigh strength low steam-to-oil ratio ethylbenzene dehydrogenationcatalyst.

BACKGROUND TECHNOLOGY

Ethylbenzene dehydrogenation is a strong endothermic, molecularincreasing reversible reaction. Water vapor is often used as a diluentto reduce the partial pressure of ethylbenzene and to move the reactiontoward the product. Water vapor in the reaction has the followingeffects:

(1) heating the reaction raw materials to the required temperature,avoiding heating ethylbenzene directly to a higher temperature andinhibiting the side reactions;

(2) adding heat, so as to avoid cooling due to endothermic reaction

(3) continuously removing coke deposit from the catalyst through thewater-gas reaction, so that the catalyst is regenerated automatically;and

(4) maintaining the stability of Fe³⁺ in the active phase of catalyst,preventing excessive reduction thereof, and maintaining the stability ofthe catalyst.

However, the amount of water vapor added is subject to two factors: theallowable pressure drop and energy consumption of the reaction system.Advanced ethylbenzene dehydrogenation processes always pursue a higheryield of styrene at a lower steam-to-oil ratio (mass ratio of watervapor to ethylbenzene in the feed). Operation under low steam-to-oilratio is one of the important measures for a styrene plant to reduceenergy consumption.

The catalyst for dehydrogenation of ethylbenzene to styrene is aniron-based catalyst wherein iron oxide is the main active component andpotassium oxide is the main promoter. Potassium can increase theactivity of iron oxide by an order of magnitude, and can promote thewater-gas reaction to remove carbon deposit and make the catalystregenerate automatically. However, potassium easily migrates and getslost during the reaction, which is an important cause for thedeactivation of the catalyst. If an average catalyst is used in thedehydrogenation of ethylbenzene under the condition of low steam-to-oilratio (water vapor/ethylbenzene), the water-gas reaction rate willdecrease and the carbon deposition on the catalyst surface willincrease, resulting in poor stability. In addition, during ethylbenzenedehydrogenation at low steam-to-oil ratio, as the partial pressure ofhydrogen in the reaction system increases and the reducibilityincreases, part of the Fe³⁺ in the catalyst will be reduced, which willcause the crystal structure of the catalyst to change, resulting in adecrease of the strength of the catalyst. However, large ethylbenzenedehydrogenation units are operated at low steam-to-oil ratio in order tosave energy. At the same time, due to their high catalyst loadingquantity, large units have higher requirement for the catalyst strengthin order to prevent the catalyst from being crushed. Researchers havemade many attempts to develop a low steam-to-oil ratio catalyst.

European Patent No. 0177832 reports that, with addition of 1.8-5.4 wt %magnesia, the catalyst demonstrates high and stable performance atsteam-to-oil ratios below 2.0 wt. %. However, the catalyst has higherpotassium content.

U.S. Pat. No. 4,535,067 discloses that a portion of the potassium in thecatalyst is added in the form of potassium nepheline doublets, but thecatalyst has a conversion rate less than 65%, selectivity no more than93% and styrene yield less than 60%, which is relatively low. Moreover,there is no reference to the life of the catalyst.

At present, in most of the disclosed low steam-to-oil ratio ethylbenzenedehydrogenation catalysts, researchers often add in a binder to improvecatalyst strength in order that the catalyst could be operated under lowsteam-to-oil ratio conditions.

Patent CN103768150 discloses a low steam-to-oil ratio ethylbenzenedehydrogenation catalyst and it's preparing method, wherein vanadium isintroduced into an iron-potassium-cerium-tungsten-magnesium system, and2 to 5% binder selected from kaolin, diatomaceous earth or cement isalso added.

Patent CN101279266A discloses an energy saving ethylbenzenedehydrogenation catalyst, wherein nickel oxide and another light rareearth oxide are added into a Fe—K—Ce—W—Mg system, and a binder selectedfrom kaolin, diatomaceous earth or cement is also added in order tomaintain the strength of the catalyst.

Patent CN101279268A discloses an energy saving ethylbenzenedehydrogenation catalyst, wherein boron trioxide and niobium oxide areadded into a Fe—K—Ce—W system, and a binder selected from kaolin,diatomaceous earth or cement is also added in order to maintain thestrength of the catalyst

Patent CN10127926A discloses a catalyst for dehydrogenation ofethylbenzene at low steam-to-oil ratio, wherein bismuth oxide andberyllium oxide are added into a Fe—K—Ce—W—Ca system, and a binderselected from kaolin, diatomaceous earth or cement is also added inorder to maintain the strength of the catalyst.

Patent CN101992094A discloses a catalyst for dehydrogenation ofethylbenzene at low steam-to-oil ratio, wherein rubidium compound andone selected from the group consisting of Pm₂O₃, Eu₂O₃, Gd₂O₃ and Dy₂O₃are added into a Fe—K—Ce—W—Ca system, and 0-4% binder selected fromkaolin, diatomaceous earth or cement is also added in order to maintainthe strength of the catalyst.

Patent CN102371161A discloses a catalyst for dehydrogenation ofethylbenzene at low steam-to-oil ratio, wherein cesium compound and oneselected from the group consisting of Sm₂O₃, Eu₂O₃, Gd₂O₃ and Dy₂O₃ intoa Fe—K—Ce—W—Mg system, and 0-4% binder selected from kaolin,diatomaceous earth or cement is also added in order to maintain thestrength of the catalyst.

Patent CN103028421A discloses a catalyst for dehydrogenation ofethylbenzene at low steam-to-oil ratio, wherein potassium molybdate isadded into a Fe—K—Ce—W—Mg system, and 2-5% binder selected from kaolin,diatomaceous earth or cement is also added in order to maintain thestrength of the catalyst.

Patent CN103537696A discloses a catalyst for dehydrogenation ofethylbenzene at low steam-to-oil ratio, wherein manganese ferrite isadded into a Fe—K—Ce—W—Mg system, and 0-4% binder selected from kaolin,diatomaceous earth or cement is also added in order to maintain thestrength of the catalyst.

Patent CN103769150A discloses a catalyst for dehydrogenation ofethylbenzene at low steam-to-oil ratio, wherein potassium vanadate isadded into a Fe—K—Ce—W—Mg system, and 2-5% binder selected from kaolin,diatomaceous earth or cement is also added in order to maintain thestrength of the catalyst.

Catalysts in the published patents above use kaolin clay, diatomite orcement as a binder. Although the binder can improve the strength of thecatalyst, the introduction of inert binder will partially cover theactive site of the catalyst, resulting in decreased activity of thecatalyst.

Patent CN1981929A discloses a low steam-to-oil ratio catalyst wherein,although no portland cement is added during the preparation of thecatalyst, the strength of the catalyst is not disclosed, and theoperation steam-to-oil ratio thereof is 1.8, which is high.

CONTENT OF THE INVENTION

In view of the poor catalyst strength and low activity at lowsteam-to-oil ratio, which are the problems of the ethylbenzenedehydrogenation catalysts in the prior art, the purpose of the presentinvention is to provide a binder-free high strength and low steam-to-oilratio ethylbenzene dehydrogenation catalyst, which has high strength andfeatures high activity at low steam-to-oil ratio, helping improve theproduction efficiency, when used in the preparation of styrene byethylbenzene dehydrogenation.

In order to overcome the deficiencies of the prior art, the technicalsolution provided by the present invention is:

A binder-free high strength, low steam-to-oil ratio ethylbenzenedehydrogenation catalyst, which comprises the following components inpercentage by weight:

(a) 60-85% Fe₂O₃;

(b) 3-25% K₂O;

(c) 0.1-5% MoO₃;

(d) 3-20% CeO₂;

(e) 0.1-5% CaO;

(f) 0.1-5% Na₂O;

(g) 0.1-5% MnO₂, wherein the weight ratio of Na₂O and MnO₂ is 0.1-10;

(h) 0.1-100 ppm of at least one element or oxide of Pb, Pt, Pd, Ag, Au,Sn;

The catalyst is not added with binder during the preparation thereof.

In a preferred embodiment, the weight ratio of Na₂O to MnO₂ is 0.2-8.

In a more preferred embodiment, the weight ratio of Na₂O to MnO₂ is0.5-5.

In a preferred embodiment, the cerium source is at least one of ceriumcarbonate, cerium oxalate, basic cerium carbonate and cerium nitrate.

In a preferred embodiment, the catalyst further contains 0.05-2% copperor zinc or magnesium oxide, as CuO, ZnO and MgO, respectively.

The raw materials for preparing the catalyst provided in the presentinvention comprise: Fe₂O₃ composed of red iron oxide (Fe₂O₃) and yellowiron oxide (Fe₂O₃.H₂O), wherein the ratio of red iron oxide to yellowiron oxide is Fe₂O₃:Fe₂O₃.H₂O=0.2-5:1, preferably 1-4.5:1; K added aspotassium salt or hydroxide; Mo added as its salt or oxide; Na added ashydroxide or sodium salt; and Pb, Pt, Pd, Ag, Au, Sn added as oxides,hydroxides or salts. In the preparation process of the presentinvention, in addition to the main components of the catalyst, porogenshould also be added, which may be selected from graphite, polystyrenemicrospheres or carboxy methyl cellulose, at an amount of 1-6% of thetotal weight of the catalyst, and no binder is added.

The preparation method of the catalyst provided by the present inventionis as follows: weigh the raw materials and porogen according to theratio, mix well and add in deionized water to prepare an adhesive paste,which is extruded into strips and cut into particles with a diameter of3 mm and a length of 8˜10 mm, dried at 60-120° C. for 24h, and finallycalcined at 400˜1000° C. for 4h.

In the present invention, the crush strength of the catalyst is measuredaccording to the technical requirements stipulated in the standard HG/T2782-1996, using a DL-II type intelligent particle strength meter, withtest samples of the length of 5 mm and in a group of 40 pieces. Thearithmetic mean of the measurement results is taken as the final crushstrength value in Newton/mm (N/mm).

In the present invention, by adding a combination of Na compound and Mncompound into the iron-potassium-cerium-molybdenum-calcium catalystsystem instead of a binder and adjusting the ratio, it is surprisinglyfound that the strength of the catalyst is greatly increased withoutnecessarily adding cement or the like inert binder; by adding traces ofat least one compound of Pb, Pt, Pd, Ag, Au and Sn, iron-potassiuminteraction is changed and the rate of potassium ion loss is reduced;and by adding copper, zinc, or Magnesium oxide, under the synergy effectof trace elements, the binding force of Fe—O bonds is improved, thereduction resistance of the catalyst at low steam-to-oil ratio isenhanced, the activity of the catalyst is high, and, when thesteam-to-oil ratio is reduced from 1.0 to 0.75, the yield of styrene isonly marginally reduced and the stability at low steam-to-oil isimproved. Therefore, it can be used in large styrene plants.

EXAMPLES

The above solution is further described with specific examples. Itshould be understood that these examples are for the purpose ofillustrating the invention and are not intended to limit the scope ofthe invention. The implementation conditions employed in the examplescan be further adjusted according to the specific manufacturer'sconditions, and the unspecified implementation conditions are usuallythe conventional experiment conditions.

The raw materials for preparing the catalyst are iron oxide red, ferricoxide yellow, potassium carbonate, manganese oxide, ammoniumheptamolybdate, calcium hydroxide, sodium carbonate, cerium sources(cerium carbonate, cerium oxalate, cerium carbonate, cerium oxide), Goldnitrate, palladium nitrate, platinum nitrate, silver nitrate, leadoxide, tin oxide, zinc oxide, copper oxide and magnesium oxide.

Comparative Example 1

The raw materials as iron oxide red, iron oxide yellow, potassiumcarbonate, cerium carbonate, ammonium heptamolybdate and calciumhydroxide were mixed in a kneader for 1 hour, added with deionized waterand stirred for 1 hour. Then the paste was extruded into particles 3 mmin diameter and 8 to 10 mm in length. The particles were dried for 2hours at 80° C. and another 2 hours at 120° C., and then placed in amuffle furnace and calcined at 900° C. for 4 hours. It is catalyst A

Catalyst A comprises 76.6% Fe₂O₃, 11.2% K₂O, 7.5% CeO₂, 2.2% CaO and2.5% MoO₃ by weight percentage. See Table 1

The activity of the catalyst prepared was evaluated in an isothermalfixed bed. The specific process is: the deionized water and ethylbenzenewere fed into the preheat mixer respectively by a metering pump, wherethey were preheated and mixed into gas and fed into the reactor; thereactor was a 1 inch stainless steel tube which can load 100 ml catalystof 3 mm particle size and was heated by electric heating wires to therequired temperature for reaction; the reaction product coming out ofthe reactor was condensed with water and the composition thereof wasanalyzed by gas chromatography; and the ethyl benzene (EB) conversionand styrene selectivity were calculated according to the followingformulas:EB conversion %=(EB concentration before reaction wt %−EB concentrationafter reaction wt %)/EB concentration before reaction wt %Styrene selectivity %=concentration of styrene wt %/(EB concentrationbefore reaction wt %−EB concentration after reaction wt %)

The reactor was loaded with 100 ml catalyst, and the catalyst activitywas evaluated at atmospheric pressure, liquid hour space velocity1.0h⁻¹, 620° C. and steam-to-oil ratio (by weight) of 1.0 and 0.75. Thetest results are shown in Table 2-3.

Comparative Example 2

It was mostly the same as in Comparative Example 1 except that sodiumcarbonate was added into the raw materials for preparing the catalyst(Catalyst B) in Comparative Example 2. The catalyst B componentcomprises, by weight percent, 75.1% Fe₂O₃, 11.2% K₂O, 7.5% CeO₂, 2.2%CaO, 2.5% MoO₃ and 1.5% Na₂O, as shown in Table 1. After the catalyst isprepared, the activity of the catalyst was evaluated according to theevaluation method of Comparative Example 1, and the test results areshown in Table 2-3.

Comparative Example 3

It was mostly the same as in Comparative Example 1 except that manganeseoxide was added into the raw materials for preparing the catalyst(catalyst C) in Comparative Example 3. The catalyst C componentcomprises 75.4% Fe₂O₃, 11.2% K₂O, 7.5% CeO₂, 2.2% CaO, 2.5% MoO₃ and1.2% MnO₂ in weight percentage.

The catalyst components are shown in Table 1. Catalyst activity wasevaluated according to the evaluation method of Comparative Example 1.The test results are shown in Table 2-3.

Working Examples 1-5

A series of catalysts, DEFGH, were prepared by adding different amountsof MnO₂, wherein the cerium source was cerium carbonate in catalyst D,cerium oxalate in catalyst E, basic cerium carbonate in catalyst F,cerium nitrate in catalyst G, and cerium oxide in the rest of thecatalysts. Pt, Pd, Ag and Au were added in the form of nitrates, and Pband Sn were added in the form of oxides. The content of sodium oxide ineach catalyst was set to 2.5%, and the amounts of other raw materialsused were in accordance with the compositions of the actual oxides shownin Table 1. After the catalyst was prepared, the catalyst activity wasevaluated according to the evaluation method of Example 1, and the testresults are shown in Table 2-3.

Working Examples 6-14

A series of catalysts I-R were prepared by adding different amounts ofMnO₂ and Na₂O. The amounts of other raw materials were according to thecompositions of the actual oxides as shown in Table 1.

TABLE 1 Catalyst Composition and strength Catalyst A B C D E F G H I J KL M N O P Q R Fe₂O₃/% 76.6 75.1 75.4 72.35 71.4 70 70.45 67 70.2 71.5574.1 73.55 69.6 68.7 74.9 69.6 72 71.6 K₂O/% 11.2 11.2 11.2 11.2 11.211.2 11.2 11.2 11.2 11.2 11.2 11.2 11.2 11.2 11.2 11.2 11.2 11.2 CeO₂/%7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5 7.5CaO/% 2.2 2.2 2.2 2.2 2.2 2.2 2.2 2.2 2.2 2.2 2.2 2.2 2.2 2.2 2.2 2.22.2 2.2 MoO₃/% 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.5 2.52.5 2.5 2.5 2.5 Na₂O/% 1.5 2.5 2.5 2.5 2.5 2.5 0.5 0.7 1.6 0.9 3.0 5 0.14.2 2.8 2.5 MnO₂/% 1.2 0.25 0.5 2.5 3.6 5.0 5 3.5 0.2 0.1 0.5 1.0 0.71.3 0.6 2.5 Na₂O/MnO₂ 10 5 1.0 0.69 0.5 0.1 0.20 8.0 9.0 6.0 5.0 0.144.0 4.7 1.0 CuO 0.2 1.0 1.1 0.8 0.05 2 0.7 1.5 ZnO 2 0.3 0.05 0.1 0.71.5 1.2 MgO 1.5 0.3 1.0 0.8 0.05 2.0 0.9 1.2 Pt/ppm 5 80 5 Pd/ppm 30 3Ag/ppm 50 66 55 60 10 PbO₂/ppm 80 100 SnO₂/ppm 60 75 30 30 Au/ppm 2 3Strength 25.2 28.1 20.2 45.2 60 70.3 66.5 65 42.2 48 49 46 51 60 45 6661 68.2 (N/mm)

As can be seen from Table 1, addition of Na₂O and MnO₂ increases thecatalyst crush strength.

Table 2 shows the performance of the catalyst at a steam-to-oil ratio of0.75.

TABLE 2 Catalyst performance at a steam-to-oil oil ratio of 0.75. Na₂OMnO₂ conversion selectivity Styrene yield Catalyst wt % wt % wt % wt %wt % A 67.8 96.1 65.2 B 1.5 67.2 95.9 64.4 C 1.2 66.5 95.8 63.7 D 2.50.25 72.4 95.9 69.4 E 2.5 0.5 74.3 96.0 71.3 F 2.5 2.5 76.6 96.5 73.9 G2.5 3.6 76.3 95.8 73.1 H 2.5 5 70.4 95.7 67.4 I 0.5 5 72.7 95.3 69.3 J0.7 3.5 72.5 95.6 69.3 K 1.6 0.2 70.4 95.5 67.2 L 0.9 0.1 72.5 96.0 69.6M 3 0.5 72.5 95.2 69.0 N 5 1 71.8 95.7 68.7 O 0.1 0.7 74.3 95.8 71.2 P4.2 1.3 70.7 95.6 67.6 Q 2.8 0.6 71.1 95.3 67.8 R 2.5 2.5 72.6 95.1 69

Table 3 shows Catalyst performance at steam-to-oil ratio of 0.75 andTable 3 shows the decrease in styrene yield ΔY when the steam-to-oilratio is decreased from 1.0 to 0.75.

TABLE 3 Catalyst performance at steam-to-oil ratio 1.0 Con- Selec-Styrene Na₂O MnO₂ version tivity yield ΔY catalyst wt % wt % wt % wt %wt % 1.0 → 0.75 A 74.6 96.2 71.8 6.6 B 1.5 75.4 95.8 72.2 7.8 C 1.2 74.595.9 71.4 7.7 D 2.5 0.25 76.3 96.0 73.2 3.8 E 2.5 0.5 77.5 96.1 74.5 3.2F 2.5 2.5 78.1 96.6 75.4 1.5 G 2.5 3.6 79.5 95.9 76.2 3.1 H 2.5 5 75.495.8 72.2 4.8 I 0.5 5 76.2 95.5 72.8 3.5 J 0.7 3.5 74.4 95.8 71.3 2.0 K1.6 0.2 73.1 95.7 70 2.8 L 0.9 0.1 75.5 96.1 72.6 3.0 M 3 0.5 75.7 95.272.1 3.1 N 5 1 75.4 95.8 72.2 3.5 O 0.1 0.7 77.4 95.7 74.1 2.9 P 4.2 1.373.2 95.7 70.1 2.5 Q 2.8 0.6 75.7 95.1 72 4.2 R 2.5 2.5 75.6 95.5 72.23.2

As can be seen from comparison of the test results of the workingexamples and comparative examples, the catalyst has high strength andgood activity at steam-to-oil ratio of 1.0. When the steam-to-oil ratiois decreased from 1.0 to 0.75, the loss of catalyst activity is smalland the catalyst is stable.

The above examples are only for illustrating the technical idea andfeatures of the present invention, which could enable those who areskilled in the art to understand and implement the contents of thepresent invention. However, they could not limit the protection scope ofthe present invention. Any equivalent transformation or modificationmade according to the spirit of the present invention shall fall withinthe protection scope of the present invention.

The invention claimed is:
 1. A binder-free high strength and lowsteam-to-oil ratio ethylbenzene dehydrogenation catalyst, comprising thefollowing components by weight percentage: (a) 60-85% Fe₂O₃; (b) 3-25%K₂O; (c) 0.1-5% MoO₃; (d) 3-20% CeO₂; (e) 0.1-5% CaO; (f) 0.1-5% Na₂O;(g) 0.1-5% MnO₂, wherein the weight ratio of Na₂O and MnO₂ is 0.1-10;(h) 0.1-100 ppm of at least one element or oxide of Pb, Pt, Pd, Ag, Au,Sn; and no binder is added during the preparation of the catalyst. 2.The binder-free high strength, low steam-to-oil ratio ethylbenzenedehydrogenation catalyst according to claim 1, wherein the weight ratioof Na₂O and MnO₂ is 0.2-8.
 3. The binder-free high strength and lowsteam-to-oil ratio ethylbenzene dehydrogenation catalyst according toclaim 2, wherein the weight ratio of Na₂O MnO₂ is 0.5-5.
 4. Thebinder-free high strength and low steam-to-oil ratio ethylbenzenedehydrogenation catalyst according to claim 1, wherein the catalystfurther contains 0.05 to 2% copper, zinc, or magnesium oxide, as CuO,ZnO or MgO, respectively.